Cavity perturbation method for characterization of liquid crystals up to 35 GHz

Liquid Crystals (LCs) are very promising agile materials for tunable microwave components [Z]. Hence, precise microwave measurements are required. In this paper the measurement results of two LCs are presented using a cavity perturbation method with two cavities at 9GHz between -25°C and 45°C and at 3SGHz between -10/sl degC and 80sl degC. The cavities are rectangular waveguide resonators with two insertion holes for LC-filled FTFE-tubes. The complex permittivity as well as the complex permeability of these samples are extracted. The tunability of the LCs are measured by using an external magnetostatic field in order to orient the LC-molecules. Besides the quasi-standard LC K15, a novel mixture is investigated, having a higher tunability and lower losses compared to K1S at microwaves.